package tech.darkblue.rpcui.editor;

import org.eclipse.jface.text.BadLocationException;
import org.eclipse.jface.text.DocumentEvent;
import org.eclipse.jface.text.IDocument;
import org.eclipse.jface.text.IRegion;
import org.eclipse.jface.text.ITypedRegion;
import org.eclipse.jface.text.Region;
import org.eclipse.jface.text.TextAttribute;
import org.eclipse.jface.text.TextPresentation;
import org.eclipse.jface.text.presentation.IPresentationDamager;
import org.eclipse.jface.text.presentation.IPresentationRepairer;
import org.eclipse.core.runtime.Assert;
import org.eclipse.swt.custom.StyleRange;

public class NonRuleBasedDamagerRepairer
    implements IPresentationDamager, IPresentationRepairer {

    /** The document this object works on */
    protected IDocument fDocument;
    /** The default text attribute if non is returned as data by the current token */
    protected TextAttribute fDefaultTextAttribute;

    /**
     * Constructor for NonRuleBasedDamagerRepairer.
     */
    public NonRuleBasedDamagerRepairer(TextAttribute defaultTextAttribute) {
        Assert.isNotNull(defaultTextAttribute);

        fDefaultTextAttribute = defaultTextAttribute;
    }

    /**
     * @see IPresentationRepairer#setDocument(IDocument)
     */
    public void setDocument(IDocument document) {
        fDocument = document;
    }

    /**
     * Returns the end offset of the line that contains the specified offset or
     * if the offset is inside a line delimiter, the end offset of the next line.
     *
     * @param offset the offset whose line end offset must be computed
     * @return the line end offset for the given offset
     * @exception BadLocationException if offset is invalid in the current document
     */
    protected int endOfLineOf(int offset) throws BadLocationException {

        IRegion info = fDocument.getLineInformationOfOffset(offset);
        if (offset <= info.getOffset() + info.getLength())
            return info.getOffset() + info.getLength();

        int line = fDocument.getLineOfOffset(offset);
        try {
            info = fDocument.getLineInformation(line + 1);
            return info.getOffset() + info.getLength();
        } catch (BadLocationException x) {
            return fDocument.getLength();
        }
    }

    /**
     * @see IPresentationDamager#getDamageRegion(ITypedRegion, DocumentEvent, boolean)
     */
    public IRegion getDamageRegion(
        ITypedRegion partition,
        DocumentEvent event,
        boolean documentPartitioningChanged) {
        if (!documentPartitioningChanged) {
            try {

                IRegion info =
                    fDocument.getLineInformationOfOffset(event.getOffset());
                int start = Math.max(partition.getOffset(), info.getOffset());

                int end =
                    event.getOffset()
                        + (event.getText() == null
                            ? event.getLength()
                            : event.getText().length());

                if (info.getOffset() <= end
                    && end <= info.getOffset() + info.getLength()) {
                    // optimize the case of the same line
                    end = info.getOffset() + info.getLength();
                } else
                    end = endOfLineOf(end);

                end =
                    Math.min(
                        partition.getOffset() + partition.getLength(),
                        end);
                return new Region(start, end - start);

            } catch (BadLocationException x) {
            }
        }

        return partition;
    }

    /**
     * @see IPresentationRepairer#createPresentation(TextPresentation, ITypedRegion)
     */
    public void createPresentation(
        TextPresentation presentation,
        ITypedRegion region) {
        addRange(
            presentation,
            region.getOffset(),
            region.getLength(),
            fDefaultTextAttribute);
    }

    /**
     * Adds style information to the given text presentation.
     *
     * @param presentation the text presentation to be extended
     * @param offset the offset of the range to be styled
     * @param length the length of the range to be styled
     * @param attr the attribute describing the style of the range to be styled
     */
    protected void addRange(
        TextPresentation presentation,
        int offset,
        int length,
        TextAttribute attr) {
        if (attr != null)
            presentation.addStyleRange(
                new StyleRange(
                    offset,
                    length,
                    attr.getForeground(),
                    attr.getBackground(),
                    attr.getStyle()));
    }
}
